The present invention relates to compound bodies and other bodies with internal channels and methods of producing the same. It applies in particular to compound tools provided with coolant channels.
Compound bodies for tools and wear parts with a hard material containing 30-70 vol% hard constituents are disclosed in Swedish patent application No. 8302735-9 and U.S. Pat. No. 4,168,540. It has according to this application surprisingly enough turned out to be possible to co-extrude two materials with different properties, particularly different deformation resistance.
In many tool applications it is desirable to deliver coolant directly to the working edge. The purpose of the coolant is not only to remove heat but also to facilitate chip removal.
Until now it has been possible down to a certain dimension, about 12 mm, to drill a hole in the core of cutting tools, such as twist drills, and then drill inclined holes from the rake faces to the centre hole. This is very expensive and, as mentioned, dimensionally limited at the lower end of the range of diameters. In such a tool it is not possible to cut and grind a new edge since in such a case a hole in the center is obtained.
A method previously used to make bodies with coolant channels is to place a coil of copper or similar material in a powder body and then sinter. The copper is herewith absorbed by the porous body when the melting point of copper is exceeded and a hole remains which can possess a complicated geometry. The disadvantages are that copper lowers the tool toughness and that slender products cannot be produced economically.
Other methods which are known employ for example wax instead of copper. Such a core of wax is melted away before the sintering of the compact takes place. A complicated wax profile, for example a helix, can, however, not be compacted into a powder body. The wax profile would be compacted into a powder body. The wax profile would be deformed due to the high compacting pressure. Other techniques therefore have to be used. One such method is first to compact a center core, put in the wax cores (after possible grooves have been made) and press an outer cover onto the powder-wax-cores.
A temporary filling such as wax and other low melting materials such as copper may prevent the body from being deformed after the removal of the temporary filling because the holes are welded together. Moreover, it is a very expensive way of obtaining holed blanks in slender dimensions.
The present invention relates to tools such as drills, end mills, threading tapes, broaches, etc., with coolant channels down to more slender dimension than previously possible on the one hand, and economical methods of obtaining these on the other.
With the present invention considerable length of slender holed bars can be obtained after only one operation comprising production of a blank with a filler material which is removed after extrusion etc and after cutting up in smaller lengths.
To provide a sufficient amount of coolant, the diameter of the channels should be more than 0.5 mm, preferably more than 1 mm.